Flame retardant fibers for textile use

ABSTRACT

The present invention pertains to thermoplastically processable synthetic polymers and fibers produced therefrom which are rendered flame retardant by certain organic pigments which are substantially unreactive with the polymer. The flame retardant materials include: 
     (i) carbon black pigment; ##STR1## (iii) a chromium 1:2 complex azo dye wherein said dye has the following formula: ##STR2##  wherein: m, n, p, and q are each either O or an integer from 1 to about 4; or, 
     (v) mixtures thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to flame retardant synthetic polymers which findparticular application in the production of filaments and fibers for usein the textile industry.

2. Description of the Prior Art

Numerous procedures have been proposed for conferring flame retardanceon melt extruded filaments or fibers for use in the textile industry,such as the construction of carpets. One procedure has been toincorporate flame retardant materials into the polymer used to make thefilaments or fibers by extruding the flame retardant material with thepolymer.

Although this procedure has proven useful in certain instances, certainproblems have remained. For instance, a number of flame retardantmaterials, when extruded with the polymer, result in finished polymershaving an undesirably colored surface. Furthermore, resulting filamentscontaining the flame retardant materials, in many cases, haveundesirable surface properties such as sensitivity to heat and light.Still further, many times the extruded material containing the syntheticpolymer and flame retardant material is sensitive at the surface whenthe filaments are processed such as by passing them over guides, drawingthem, or thermally treating them.

Another problem associated with a number of commercially available flameretardant materials is that it is necessary to incorporate largeamounts, i.e., 20 to 40% by weight of the flame retardant, into thesynthetic polymer. As a result, the physical properties of the syntheticpolymer are modified which can result in the production of inferiorfibers. Also, the incorporation of large amounts of flame retardant isuneconomical.

The term fiber as used herein includes fibers of extreme or indefinitelength (i.e., filaments) and fibers of short length (i.e., staple). Theterm yarn, as used herein, means a continuous strand of fibers.

Carpet made from fibers of synthetic polymers, such as nylon fibers, isa popular floor covering for both residential and commercialapplications. The typical carpet for residential applications has aprimary backing material such as polypropylene, stretched with closelyspaced erect loops or cut loops of yarn which extend upwardly from thebacking to form a tufted structure (i.e., pile).

It is important that carpet have a combination of qualities, includingsafety, and aesthetically pleasing. Therefore, it is important that thefibers used for the carpet be fire retardant and not contain asignificant amount of undesirable surface properties.

Thus, there is a need for materials which impart flame retardance tosynthetic polymers used for fiber or yarn production without aconcomitant reduction of physical properties of the fiber or yarn andwhich are effective in minor amounts such that commercially acceptableproducts are produced.

SUMMARY OF THE INVENTION

It has been surprisingly discovered that flame retardant polymercompositions can be prepared by incorporating into a thermoplastically,processable synthetic polymer minor amounts of certain organic pigmentswhich are substantially nonreactive with the synthetic polymer. Theresulting polymer compositions have excellent flame retardant propertieswhile retaining excellent physical properties of the resulting syntheticpolymers.

Fibers and yarns produced from the synthetic polymer find particularapplication in the textile industry such as in the construction ofcarpets.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The organic pigments useful in the present invention include:

(i) carbon black pigment; ##STR3##

(iii) a chromium 1:2 complex azo dye wherein said dye has the followingformula: ##STR4##

m, n, p, and q are each either 0 or an integer from 1 to about 4; and,mixtures thereof.

Preferably, in the compounds represented by formula III, the sum of m,n, p, and q is either 0 or an integer of 1, 15, or 16. These compoundshave the following formulae: ##STR5##

Preferably, the carbon black pigments of the present invention have aparticle size (arithmetic mean diameter) in the range of from about 10nanometers to about 100 nanometers and, preferably, a particle size inthe range of from about 15 to 60 nanometers. A preferred carbon blackpigment is a furnace type of carbon black which is available from CabotCompany under the name Raven 1200.

Preferably, the methyl groups occupy the para position and one orthoposition of the aniline moieties of formula I as set forth in thefollowing structure ##STR6##

The preparation of the compound represented by formula I is known topersons skilled in the art. For instance, the compound can be preparedby condensing 2,4-dimethylaniline with 3,4,9,10-perylenetetracarboxylicacid. The compound is sometimes referred to as C.I. Pigment Red 149, andis available commercially from BASF Corporation as Paliogen Red K-3580.

The preparation of the chromium complex azo dyes is well known topersons skilled in the art. U.S. Pat. Nos. 4,598,020 and 4,005,066,which are assigned to the assignee of the present invention and arehereby incorporated by reference, disclose its preparation. The complexis commercially available from BASF Wyandotte Corporation as Zaponyellow 157.

The preparation of compounds represented by formula III is well known topersons skilled in the art. For example, see U.S. Pat. Nos. 2,276,860and 2,214,469, which are hereby incorporated by reference.

The compound represented by formula IV is sometimes referred to as C. I.Pigment Green 7, and is commercially available from BASF Corporation asHeliogen Green K-8683. The compound represented by formulae IV and/or Vis sometimes referred to as C.I. Pigment 15, and is commerciallyavailable from BASF Corporation as Heliogen Blue as D-7080.

The effective amount of flame retardant required to be added to thesynthetic polymer is somewhat dependent on the flame retardant andpolymer utilized. A sufficient amount of retardant should be utilized toimpart flame retardance to the polymer, but an excess that willadversely effect the polymer properties should be avoided. The optimumamount for each combination of polymer and retardant can be readilydetermined by one skilled in the art. In general, from about 0.5 toabout 5.0% based on the weight of the polymer, preferably about 1.0 toabout 3.0 percent, is utilized.

Examples of synthetic polymers suitable for use in the invention includesynthetic thermoplastic polymers which are capable of being meltextruded as fibers including polyolefins, for example, homopolymers ofolefins such as low-density polyethylene, high-density polyethylene,polypropylene, and the like, and copolymers of olefins with otherethylenically unsaturated monomers such as ethylene-propylene copolymer,ethylenebutene copolymer, ethylene-vinyl acetate copolymer,styrene-butadiene copolymer, acrylonitrile-styrene-butadiene copolymerand the like.

Polyamides find particular application in the present invention.Examples of such polyamides include homopolyamides and copolyamideswhich are obtained by the polymerization of lactam or aminocaprionicacid or a copolymerization product of diamine and dicarboxylic acid.

Typical polyamides include nylon 6, nylon 6,6, nylon 6,10, nylon 6,12,nylon 11, nylon 12, and copolymers thereof or mixtures thereof.Polyamides can be also copolymers of nylon 6 or nylon 6,6 and a nylonsalt obtained by reacting a dicarboxylic acid component such asterephthalic acid, isophthalic acid, adipic acid and sebacic acid with adiamine such as hexamethylenediamine, methaxylenediamine, and1,4-bisaminomethylcyclohexane.

Polyester also finds particular application in the present invention.The preferred polyesters are the linear terephthalate polyesters, i.e.,polyesters of a glycol containing from 2 to 20 carbon atoms and adicarboxylic acid component comprising at least about 75% terephthalicacid. The remainder, if any, of the dicarboxylic acid component may beany suitable dicarboxylic acid such as sebacic acid, adipic acid,isophthalic acid, sulfonyl-4,4-dibenzoic acid, or2,8-di-benzofurandicarboxylic acid. The glycols may contain more thantwo carbon atoms in the chain, e.g., diethylene glycol, butylene glycol,decamethylene glycol, and bis-1,4-(hydroxymethyl) cyclohexane. Examplesof linear terephthalate polyesters which may be employed includepoly(ethylene terephthalate), poly(butylene terephthalate),poly(ethylene terephthalate/5-chloroisophthalate)-(85/15), poly(ethyleneterephthalate/5-[sodium sulfo]isophthalate)(97/3),poly(cyclohexane-1,4-dimethylene terephthalate), andpoly(cyclohexane-1,4-dimethyleneterephthalate/hexahydroterephthalate)(75/25).

Other additives commonly used in the preparation of fibers may also bepresent in the proportion that they are commonly used. Examples of suchadditives include delustrants, stabilizers, antimicrobials, andantistatic agents.

A particular advantage of the flame retardants of the present inventionis that they function as a pigment in addition to their flame retardancyability. Thus, the retardant provides a dual purpose. In addition, theretardants can be used with pigments which do not have a flameretardancy capability, and the resulting polymeric material stillexhibits excellent flame retardancy.

The synthetic polymer and flame retardant are preferably melt-processedinto fibers by procedures known to persons skilled in the art. Forexample, a mixture of synthetic polymer and flame retardant aretypically extruded at a temperature above the melting point of themixture, in the case of nylon 6 above 255 degrees Centigrade, through aspinneret to form a number of molten streams. The molten streams areprocessed by standard procedures known to one skilled in the art toconverge the formed fibers into yarn. In many instances, the moltenstreams are preferably quenched in an inert atmosphere, i.e., anatmosphere substantially free of oxygen such as a nitrogen, steam, orcarbon dioxide atmosphere.

It has been surprisingly found that the fire retardancy of the materialsof the present invention can be further enhanced by applying, generallyby coating the fiber surface, a spin finish that acts as a lubricant orantistatic agent and which comprises an organic chemical having low orno volatility. Examples of such chemicals include MAGIC, a product ofLutex Chemical Corporation, and Stantex N-7601, a product of StandardChemical Products. It is believed that the chemical sold as MAGICcomprises a polyelectrolytic complex comprising a quarternized coconutoil fatty acid amine and a polyolefin, such as polyethylene orpolypropylene having an anionic functional group such as a carboxylgroup. When utilized, these chemicals are preferably applied to thefiber in a 5.0% by weight aqueous solution, and, to the fiber, an amountof about 0.15 weight percent based on the weight of the fiber orfilament.

The following examples will serve to more comprehensively illustratecertain specific embodiments of the invention, but are not intended tobe construed so as to be restrictive of the spirit and scope thereof.

EXAMPLES

The flame retardancy of fibers of the present invention was tested usingthe procedure described in Fed. Test Method Std. No. 372, dated Aug. 31,1977, and entitled "TEST FOR CRITICAL RADIANT FLUX OF CARPET FLOORINGSySTEMS (FLOORING RADIANT PANEL TEST)" which is hereby incorporated byreference. The method of the test involves a procedure for measuring thecritical radiant flux at flameout of horizontally mounted carpet floorcovering systems exposed to a flaming ignition source in a gradedradiant heat energy environment, in a text chamber. The imposed radiantflux simulates the thermal radiation levels likely to impinge on thefloors of a building whose upper surfaces are heated by flames and/orhot gases from a fully-developed fire in an adjacent room orcompartment. The test, which was developed to simulate an important fireexposure component of fires which may develop in corridors or exitwaysof buildings, is different from many other fire test methods, in that itmeasures an actual property of the carpet system and is not based on anarbitrary scale.

Critical Radiant Flux is the level of incident radiant heat energy onthe carpet floor covering system at the most distant flameout point. Itis reported as watts/cm² (Btu/ft² sec). It is determined by measuringthe distance that the carpet is burned, i.e., the point of farthestadvance of the flame front, to the nearest 0.1 cm.

Government recommended minimum critical flux limits are: 0.45 watts/cm²within corridors and exitways of hospitals and nursing homes, and 0.22watts/cm² within corridors and exitways of other occupancies except one-and two-family dwellings. These limits are described in the publication"NATIONAL BUREAU OF STANDARDS, U.S. DEPARTMENT OF COMMERCE, PUB. NO.NBSIR-78-1436, FLAMMABILITY TESTING FOR CARPET" (April 1978), which ishereby incorporated by reference.

The basic elements of the test chamber used in the tests are (1) anair-gas fueled, radiant heat energy panel inclined at 30 degrees to anddirected at (2) a horizontally mounted floor covering system specimen.The radiant panel generates a radiant energy flux distribution rangingalong the 100 cm length of the test specimen from a nominal maximum of1.0 watts/cm² to a minimum of 0.1 watts/cm². The test is initiated byopen flame ignition from a pilot burner. The distance burned to flameoutis converted to watts/cm² from a flux profile graph, set forth in testprocedure and reported as critical radiant flux, watts/cm².

EXAMPLE I

An amount of 56.25 grams of C.I. Pigment Red 149 concentrate (20% byweight) was mixed together with 1068.75 grams of Nylon 6 chips to yielda 1.0% by weight pigment concentration. The mixture was melt extrudedunder pressure of 1400 psi through a 28 orifice spinnerette to produce afiber having about 1500 denier. In addition, the spin finish describedin Example VII was also utilized. Four ends of 1500/28 feed yarn weredrawn at 3.5 times the extruded length and textured with a hot air jetto produce yarn suitable for use in carpet. This yarn is hereinafterreferred to as "yarn A". A control yarn containing no C.I. Pigment Red149 or other flame retardant material was prepared in the same manner asdescribed below. This yarn is hereinafter referred to as "yarn B".

The yarns were then two-plied by twisting two ends together with a 1.55twist. The yarns were tufted into a level loop 28 oz/yd² carpet at abouta 0.9 stitch/inch rate. A black Polybac polypropylene fabric was used asprimary backing. Tufting was carried out on a conventional tuftingmachine operated to give level loop pile having a height of 1/8 inches.

The carpets were latex and secondary jute backed by conventional meansat a rate of 30 oz/yd² of carpet on a dry basis. The latex was thencured at 125 degrees Centigrade.

The carpets were then tested to determine the distance burned and thecritical energy necessary to propagate the flame as measured by FederalTest Method Standard No. 372, dated Aug. 31, 1977. The results of thesetests are shown in Table I.

                  TABLE I                                                         ______________________________________                                                                  Critical Radiant Flux                               Carpet System                                                                            Distance Burned (cm)                                                                         Watts/cm.sup.2                                      ______________________________________                                        Made with yarn A                                                                         35             0.62                                                Made with yarn B                                                                         82             0.13                                                ______________________________________                                    

It can be seen from the above results that distance burned of a carpethaving yarns made from nylon and C.I. Pigment Red 149 as a flameretardant had excellent flame retardant properties. The flame retardantproperties were better than both government recommended requirements.

EXAMPLE II

A flame retardant carpet was prepared by the same procedure as describedin Example I except that during draw texturing two ends of 1500/28 feedyarn containing C.I. Pigment Red 149 and two ends of 1500/28 feed yarnwithout any flame retardant materials were used. The resulting carpetwas tested in accordance with the previously described test. The resultsare reported in Table II below.

                  TABLE II                                                        ______________________________________                                        Distance Burned                                                                              Critical Radiant Flux                                          (cm)           Watts/cm.sup.2                                                 ______________________________________                                        52             0.32                                                           ______________________________________                                    

The results of these tests demonstrate the excellent flame retardantproperties of yarn containing fibers containing the flame retardantmaterial and fibers not containing flame retardant material.

EXAMPLE III

A flame retardant carpet was prepared by the same procedure as describedin Example I except that 1.0% by weight C.I. Pigment Blue 15 was mixedwith nylon chips. The resulting carpet was tested in accordance with thepreviously described test. The results are reported below in Table III.

                  TABLE III                                                       ______________________________________                                        Distance Burned                                                                              Critical Radiant Flux                                          (cm)           Watts/cm.sup.2                                                 ______________________________________                                        39             0.54                                                           ______________________________________                                    

EXAMPLE IV

A flame retardant carpet was prepared by the same procedure as describedin Example I except that 1.0% by weight C.I. Pigment Green 7 was mixedwith nylon chips. The resulting carpet was tested in accordance with thepreviously described Critical Radiant Flux Test. The results arereported below in Table IV.

                  TABLE IV                                                        ______________________________________                                        Distance Burned                                                                              Critical Radiant Flux                                          (cm)           Watts/cm.sup.2                                                 ______________________________________                                        44             0.46                                                           ______________________________________                                    

EXAMPLE V

A flame retardant carpet was prepared by the same procedure as describedin Example I except that 1.0% by weight of carbon black pigment, Raven1200, was mixed with the nylon chips. The resulting carpet was tested inaccordance with the previously described Critical Radiant Flux Test. Theresults are reported below in Table V.

                  TABLE V                                                         ______________________________________                                        Distance Burned                                                                              Critical Radiant Flux                                          (cm)           Watts/cm.sup.2                                                 ______________________________________                                        40             0.52                                                           ______________________________________                                    

The results in Tables III through V demonstrate the effectiveness of thefire retardants of the present invention.

EXAMPLE VI

A flame retardant carpet was prepared by the same procedure as describedin Example I except that 0.55% by weight of Filament yellow 4G, 0.36C.I. Pigment Red 149 and 0.09% Raven 1200 was mixed with the nylonchips. Filament Yellow 4GO is an organic pigment that does not exhibitany appreciable fire retardant properties. The resulting carpet wastested in accordance with the previously described Critical Radiant FluxTest. The results are reported below in Table VI.

                  TABLE VI                                                        ______________________________________                                        Distance Burned                                                                              Critical Radiant Flux                                          (cm)           Watts/cm.sup.2                                                 ______________________________________                                        43             0.47                                                           ______________________________________                                    

The results reported in Table VI demonstrate the effectiveness of fireretardant materials of the present invention even when yarns containingorganic pigments that do not have any appreciable fire retardantproperties are included with them.

EXAMPLE VII

The fire retardants of the present invention and spin finishescomprising organic chemicals having low or no volatility were tested ontufted carpets containing nylon fibers containing the fire retardants ofthe invention.

In some of the tests, the nylon fibers of the carpets were scoured toremove the spin finish from their surface. The finish used comprised 0.6percent by weight Stantex N-7601 and 0.14 percent by weight MAGIC. Theresulting carpets were tested in accordance with the previouslydescribed Critical Radiant Flux Test. The results are reported in TableVII.

                  TABLE VII                                                       ______________________________________                                                     Critical Radiant Flux (Watts/cm.sup.2)                           Retardant Pigment Used                                                                       Scoured    Nonscoured                                          ______________________________________                                        C.I. Pigment Black 7                                                                         0.50       0.52                                                C.I. Pigment Green 7                                                                         0.30       0.52                                                C.I. Pigment Red 149                                                                         0.16       0.56                                                C.I. Pigment Blue 15                                                                         0.49       0.58                                                Average        0.36       0.55                                                ______________________________________                                    

The results of these tests demonstrate the effectiveness of the finishesin increasing the fire retardancy of fibers containing the fireretardants of the present invention.

Although the invention has been described in conjunction with preferredand alternate embodiments thereof, it is evident that many alternatives,modifications, and variations of the invention will be apparent to thoseskilled in the art in light of the foregoing description. Accordingly,it is intended to embrace within the invention all such alternatives,modifications, and variations that fall within the spirit and scope ofthe appended claims.

What is claimed is:
 1. A method of preparing one or more flame retardantfibers comprising:(a) incorporating into a thermoplastically processablesynthetic polymer a flame retardant amount of a flame retardant materialconsisting essentially of a chromium 1:2 complex azo dye having thefollowing formula: ##STR7## (b) melt processing said synthetic polymerand said fire retardant material of step (a) into said one or morefibers.
 2. The method recited in claim 1 wherein said thermoplasticprocessable synthetic polymer is selected from the group consisting ofpolyolefins, polyamides, polyesters, and mixtures thereof.
 3. The methodrecited in claim 2 wherein said flame retardant material is present insaid flame retardant composition in an amount in the range of 0.5 toabout 5 weight percent based on weight of said polymer.
 4. The methodrecited in claim 3 wherein said synthetic polymer is selected from thegroup consisting of polyethylene terephthalate, polyethylene,polypropylene, nylon 6, nylon 6,6, and mixtures thereof.
 5. The methodrecited in claim 4 wherein said resulting fibers have a critical radiantflux of at least 0.22 watts/cm².
 6. The method recited in claim 5wherein flame retardant material is present in said synthetic polymer inan amount in the range of from about 1.0 to 3.0 weight percent based onthe weight of said polymer.
 7. The method recited in claim 6 whereinsaid synthetic polymer is nylon
 6. 8. The method recited in claim 7wherein said one or more fibers have a critical radiant of at least 0.45watts/cm².
 9. The method recited in claim 1 further comprising coatingsaid one or more fibers of step (b) with a polyelectrolytic complexcomprising a quaternized coconut oil fatty acid amine and polyethyleneor polypropylene having an anionic functional group.
 10. A fireretardant yarn comprising the fibers prepared in accordance withclaim
 1. 11. A carpet having a pile comprising the fibers prepared inaccordance with claim
 1. 12. The method of preparing one or more flameretardant nylon 6 fibers having a critical radiant flux of at least 0.22watts/cm, comprising:(a) incorporating into nylon 6 from about 0.5 toabout 5 weight percent based on the weight of said nylon 6 of a flameretardant material consisting essentially of a chromium 1:2 complex azodye having the following formula: ##STR8## (b) melt processing saidnylon 6 and said fire retardant material of step (a) into said one ormore fibers; and, (c) coating said one or more fibers of step (b) with apolyelectrolytic complex comprising a quaternized coconut oil fatty acidamine and polyethylene or polypropylene having an anionic functionalgroup.
 13. A flame retardant yarn comprising said flame retardant nylon6 fibers recited in claim 12 and nylon 6 fibers without flame retardantmaterial.